Neurostimulation systems comprising implantable neurostimulation leads are used to treat chronic pain. Conventional implantable peripheral neurostimulation leads are designed for placement in the spinal canal as part of a spinal cord stimulation system, and for the therapeutic purpose of treating various forms of chronic back and extremity pain.
Until the present invention, implantable neurostimulator systems for head pain essentially involved deep brain stimulators, where leads were positioned in the substance of the brain itself; traditional spinal cord stimulator systems that were adopted and adapted for the treatment of head pain; or implantable systems for neurostimulation of the vagus nerve or sphenopalatine ganglion.
Historically, the most common case involves the adaption of spinal cord stimulators for the purpose of peripheral nerve stimulation, such that all publically available implantable neurostimulation systems utilized for the treatment of chronic head pain have been originally designed specifically as spinal cord stimulator systems for the therapeutic purpose of treating chronic back and extremity pain. As these systems were developed for implantation in the back, their design did not contemplate the anatomic and physiologic features unique to the head and chronic head pain, which are so significantly different from the anatomy of the spinal canal, and pathophysiology of chronic back pain, that when spinal cord stimulators were utilized for cranial implants, the clinical problems associated with these differences ultimately manifested themselves.
These well-documented and clinically significant problems relate to issues of patient safety and satisfaction, including the risk of an inadequate, or suboptimal, therapeutic response; issues with patient comfort and cosmetics; and an increased risk of surgical complications and technical problems. Several specific inherent deficiencies in device design and method of implant underlie these deficiencies and problems. Likely the most common methodological deficiency is the fact that the implantable pulse generator (IPG) must necessarily be implanted at a considerable anatomic distance for the cranial lead implants. Indeed, the leads must pass from their distal cranial implant positions across the cervical region and upper back to the IPG implant location, which are most commonly in the lower back, lower abdomen, or gluteal region. The related problems are due the fact that the leads must cross multiple anatomic motion segments (neck and back). Here, the simple motions of normal daily life produce adverse tension and torque forces on the leads across these motion segments, which in turn increase the risk of technical problems, including lead migration and/or lead fracture. A second problem relates to the relatively large size of the IPG, which contributes to local discomfort, cosmetic concerns, and the fact that should the IPG pocket become infected, the related clinical problem parallels the relatively large size of the IPG; that is, the larger the IPG, the larger the pocket, and the larger and more problematic any complicating infection. Additional inherent problems include the added risks, especially infection, wound dehiscence, discomfort, and cosmetic problems associated with the multiple additional incisions that are necessary to pass the leads from the IPG to their terminal positions in the head.